Laws and Exceptions.
Morin's experiments are not true for very heavy loads or at
high velocities with much abrasion. For the first, Ball gives
Fn = -9 + -266 P
for wood on wood, and the relation is set out in Fig. 571, the
dotted line shewing the result of the ordinary formula with
As regards velocity, at the Brighton brake trials, 1878, the
following results were obtained when the static coefficient was -242.
Vel. ft. per sec.
ju between brake and wheel.
fji between wheel and rail.